Javascript:通过文本字段输入计算余额和预付款

Question

我是 JavaScript 初学者。我有代码，用户可以通过该代码在输入字段中输入值(“输入给定的费用”)。我想要的是，如果用户输入超过“1000”，那么预付值应该出现在另一个输入文本中(“预付费”)。

如果用户输入的内容少于“1000”，则余额应包含在另一个文本输入中(“余额费用”)。

我的Fiddle延续了我的工作方式。

我的 Html 表单是:

 <form>
<div class="tbl_admission_FormCell">Given Fees</div> 
  <div class="tbl_admission_FormCell" style="padding:10px;"><input type="text" name="given_fees" value="" id="given_fees" onkeypress="givenfees()" onkeyup="givenfees()"/> </div> 

<div class="tbl_admission_FormCell">Balance Fees</div> 

<div class="tbl_admission_FormCell"><span id="balance_fees"></span> </div>

 <div class="tbl_admission_FormCell">Advance Fees</div> 

 <div class="tbl_admission_FormCell"><span id="advance_fees"></span> </div>
 <div class="tbl_admission_FormRow"> 
  <div class="tbl_admission_FormCell">Total Fees</div>
    <div class="tbl_admission_FormCell"><input type="text" id="total_fees" name="total_fees" style="border:none;" value="1000" readonly/></div> 
  <div class="tbl_admission_FormCell"><div class="amt_total" onchange="amt_total()" ></div></div>
  </div>
</form>
<script>
function givenfees(){
    var given_fees = document.getElementById("given_fees");
    var s = given_fees.value;
    bal_value = +s - +result;       
    var balance_fees = document.getElementById("balance_fees");
    if(+bal_value<0 )
    {
    advance_fees.innerText = +bal_value;
    }
    else
    {balance_fees.innerText = +bal_value;}
}
</script>

Answer 1

我已经编辑了您的答案。请查看fiddle 。如果我准确理解您的问题，希望这会对您有所帮助。

function givenfees(){ 
    var result=1000;
    var given_fees = document.getElementById("given_fees");
    var s = given_fees.value;
    bal_value = +s - +result;    
    var balance_fees = document.getElementById("balance_fees");
    if(+bal_value>0 )
    {
    advance_fees.innerText = +bal_value;
    balance_fees.innerText = 0;
    }
    else
    {
    balance_fees.innerText = +bal_value;
    advance_fees.innerText = 0;
    }
}